Many manufacturing treatment and combustion processes produce gases that include gaseous nitrogen oxides (NOx) and other undesirable gaseous products. For example, processes for acid pickling stainless steels and other alloys, which typically involve immersing the alloys for a time in a bath of a strongly acidic solution including nitric acid, result in gases above the bath that include NOx. Federal and local environmental laws may limit the content of NOx that is discharged into the atmosphere. In the past decades, manufacturing companies have undertaken considerable efforts to reduce the amount of NOx discharged into the atmosphere.
One known method of removing NOx from a gas stream includes contacting the gas stream with ozone to thereby oxidize the NOx in the gas stream and form oxidation products such as nitrogen sesquioxide and nitrogen pentoxide. The oxidation products produced by the ozone treatment may be collected using aqueous scrubbers, for example, stored on-site, and discarded as a liquid waste stream. Discarding the liquid waste material may require third-party waste collection and disposal services.
It would be advantageous to provide an alternative method for removing NOx from the gases produced in an alloy pickling process or other manufacturing treatment or combustion process that results in a reduced amount of waste. More generally, it would be advantageous to provide a method for removing NOx from a gas stream produced in any process and that results in a reduced amount of waste.